Antimicrobial nonwoven fabric

ABSTRACT

The present invention relates to woven or nonwoven fabric material having antimicrobial activity, and to its uses ranging from wound dressing, facial masks, surgical drapes and surgical clothing, to filter materials and similar applications where the antimicrobial effects are employed, as well as to a process for the preparation of the woven or nonwoven fabric material.

The present invention relates to a nonwoven fabric which possesses antimicrobial properties and is useful in applications where the growth of microorganisms should be inhibited, such as surgical drapes, medical devices and clothing, filters for air handling and specific antimicrobial packaging materials.

BACKGROUND OF THE INVENTION

In recent years, the increased occurrence of hospital-acquired infections has had serious implications for both patients and healthcare workers. Hospital-acquired infections typically originate in a hospital or long-term care setting. Consequently, hospitals and other healthcare facilities extensively use materials impregnated or otherwise foreseen with antimicrobial agents for a variety of topical applications, such as wound dressings and drapes, and/or sterile drapes and articles that need to be discarded after a short usage due to infection risks.

Surgical drapes are presently made from nonwoven fabrics, and are typically used during surgical procedures to isolate the patient from the operating room personnel and the environment of the operating room. Contact with contaminated liquids through surgical drapes has been considered as a primary source of bacterial contamination for patients.

Typically, drapes equipped with chemical antimicrobial agents are employed to avoid this, which typically must be present at a relatively high concentration to achieve the desired level of efficacy. The use of antibacterial or antifungal agents in non-woven fabrics is for instance disclosed in U.S. Pat. No. 4,111,922. Unfortunately, however, the required high levels of antimicrobial agents employed are undesired in many cases. For instance, the use of high levels of certain types of antimicrobial agents may be undesired due to an increased likelihood of contacting sensitive areas, such as wounds. And even if a patient does not suffer from adversary effects from contact with a chemical antimicrobial agent, most presently employed antimicrobial compositions loose efficacy over time, since the microbiological pathogens develop resistance, such as for instance exemplified by methicilin-resistant staphylococcus aureus (MRSA). This resistance spread is exacerbated by the low number of antibiotics in the development pipeline which could result in a major world-wide public health problem.

Various substrates coated with nanosilver particles or impregnated with sivler salts have been reported to develop antimicrobial properties, as for instance as disclosed by Ronen Gottesman et al, Langmuir, 2011, 27 (2), pp 720-726. However, the use and application of silver salts, or colloidal silver particles usually requires the use of complex application technologies, e.g. sonochemical application or impregnation with dispersions, which—if applicable at all due to the sensitivity of in particular non-woven materials to water or solvents—requires handling of solvents and their removal, as well as drying of the obtained products. For instance, a commonly reported approach involves to reduce a solution of silver nitrate and to deposit the silver particles on a polymeric fibre, e.g. nylon, via a process referred to as electroless deposition. The obtained silver laden polyamide is attached to a subsequent fibre layer. This renders the application process complex and cumbersome. Furthermore, the silver particles will be distributed over the whole material and not available at the contact area with moisture, such as in skin contact. Therefore, in order to be effective, such materials require a relatively high silver loading, which makes a widespread use prohibitively difficult. Yet further, due to the complexity and nature of this process, it is difficult to control the amount of silver deposited on the fibre and furthermore, the amount of silver deposited is limited by the surface area of the fibre.

Other attempts have been made to apply silver salts on the surfaces of fabrics and yarns with little success in terms of controlled release of the silver ions to the wound, while maintaining adequate absorption capabilities.

Thus, a topical treatment with metal-based antimicrobial agents has not been successfully developed and applied to a substrate having the combination of characteristics described herein, as desired for an effective wound care device. A topical treatment for textile substrates, such as a woven or nonwoven fabric, would be highly since it would permit treatment of the fabric after weaving, knitting, and similar processes, in order to provide greater versatility to the target fibre without altering its physical characteristics.

This is also advantageous for application to porous or foam materials because antimicrobial agents are not incorporated into the material in areas that will never come into contact with the microbial pathogens.

Likewise, hospitals, and generally facilities sensitive to microbiological pathogens have been increasingly facing issues with microbiological contamination of the air, spread through building air handling systems, specifically in Heating Ventilating and Air Conditioning (HVAC) systems. HVAC system components usually operate in a warm, dark and humid environment, which makes it an ideal breeding ground for microbes such as bacteria and/or fungi. The microbiological contamination cause odour in their mildest form, but generally may cause much graver issues. This is in particular relevant as building air handling and ventilation is increasingly employed.

The microbial contamination frequently found includes fungi such as Aspergillus spp., Fusarium spp., Penicillium chrysogenum and/or Candida albicans, but also Legionella, a pathogenic Gram negative bacterium, including species that cause legionellosis or “Legionnaires' disease”, most notably, Legionella pneumophila, has caused many issues with infections transmitted through HVAC systems.

The presence of such pathogens is usually treated in various ways, including adding microbial chemical agents into the humid sections of HVAC systems. Accordingly, the use of filters and other parts in HVAC or general air handling systems, in particular filter elements with intrinsically antimicrobial activity would be highly advantageous.

As such, a need currently exists for equipping materials such as gloves, bedding textiles, surgical drapes, table paper, gowns, and facial masks, drape sheets, and others such as air and water filters with high and continuous antimicrobial activity at a relatively low level of an antimicrobial agent. Furthermore, this would allow storing such materials under non-sterile conditions.

Applicants have now surprisingly found that fabrics, both woven and non-woven, with antimicrobial activity can be provided by a simple process which permits to prepare and/or convert the materials with high quality, high antimicrobial activity and low costs.

Accordingly, the present invention relates to a fabric material having antimicrobial activity, comprising: (a) a woven or non-woven fabric material, and (b) a metal layer comprising copper and/or alloys thereof deposited on the fabric material having a thickness of from 5 to 100 nm, which layer is preferably applied under high vacuum conditions. Preferably, the metal layer also comprises silver and/or aluminium.

The thickness of the metal layer is preferably measured by Inductively coupled plasma atomic emission spectroscopy (ICP-AES), also referred to as inductively coupled plasma optical emission spectrometry (ICP-OES). This is a type of emission spectroscopy that uses the inductively coupled plasma to produce excited atoms and ions that emit electromagnetic radiation at wavelengths characteristic of a particular element. The intensity of this emission is indicative of the concentration of the element within the sample, and hence the thickness of a layer.

The term “antimicrobial activity” as used herein refers to a material that destroys, inhibits or prevents the propagation, growth and multiplication of unwanted microbial organisms.

The term “microbial organisms” or “microbes” includes, but is not limited to, microorganisms, bacteria, undulating bacteria, spirochetes, spores, spore-forming organisms, gram-negative organisms, gram-positive organisms, yeasts, fungi, moulds, viruses, aerobic organisms, anaerobic organisms and mycobacteria.

Specific examples of such organisms include the fungi Aspergillus niger, Aspergillus flavus, Rhizopus nigricans, Cladosporium herbarium, Epidermophyton floccosum, Trichophyton mentagrophytes, Histoplasma capsulatum, and the like; bacteria, such as Pseudomonas aeruginosa, Escherichia coli, Proteus vulgaris, Staphylococcus aureus, Staphylococcus epidermis, Streptococcus faecalis, Klebsiella, Enterobacter aerogenes, Proteus mirabilis, other gram-negative bacteria and other gram-positive bacteria, mycobactin and the like, as well as yeasts, such as Saccharomyces cerevisiae, Candida albicans, and the like. Additionally, spores of microorganisms, viruses and the like are microbial organisms within the scope of the present invention.

Preferably, the metal layer that imparts the antimicrobial activity comprises copper and/or silver in an amount of at least 10%, preferably 15% as calculated on the other metal(s) by weight. The metal composition preferably comprises at least copper, and/or copper alloys. Applicants found that surprisingly, copper and/or copper alloys to have at least the same or even higher antimicrobial activity than silver or silver alloys not comprising copper.

The present invention also advantageously relates to woven and nonwoven fabric materials, whereby copper or alloys thereof, however not comprising silver, have been vacuum deposited onto the fabric material; the vacuum deposition for this preferred embodiment of the invention may be any suitable vacuum deposition process, including sputtering processes. However, thermal evaporation deposition processes are strongly preferred also for these materials.

The metal composition also depends on the application process, and on the specific antimicrobial activities targeted. In this process, the metals or metal alloys are evaporated by thermal evaporation under high vacuum conditions, as those usually applied in a vacuum metallisation process.

Suitable copper alloys, provided that they can be vaporised and deposited under the desired process conditions, include the following (as specified under the European Standards for Copper and Copper Alloys): Cu-OFE, Cu-OF, CuAg0.04(OF), Cu-ETP, Cu-FRHC, Cu-ETP-1, CuAg0.04, CuAg0.07, CuAg0.10, Cu-DLP, CuAg0.10P, Cu-DHP, Cu—C, Cu-DHP, Cu-FRTP, CuTeP, CuZr, CuCd1.0, CuBe1.7, CuBe2, CuCo2Be, CuNi2Be, CuMg0.5, CuNi1P, CuFe2P, CuZn5, CuZn10, CuZn15, CuZn20, CuZn28, CuZn30, CuZn30As, CuZn36, CuZn40, CuSn3Zn9, CuZn19Sn, CuZn28Sn1As, CuSn5, CuSn4, CuSn6, CuSn8, CuAl8Fe3, CuAl10Fe1, CuAl10Ni5Fe4, CuAl10Ni5Fe4, CuMn11Al8Fe3Ni3-C, CuSi1, CuSi3Mn1, CuSi3Mn1, CuZn20Al2As, CuZn13Al1Ni1Si1, CuNi3Si1, CuNi1Si, CuNi10Fe1Mn, CuNi10Fe1Mn, CuNi10Fe1Mn1-B, CuNi25, CuNi30Mn1Fe, CuNi30Mn1 Fe, CuNi30Fe2Mn2, CuNi9Sn2, CuNi18Zn20, CuNi12Zn24, Cu—C, Cu—OF, Cu—C, Cu—C, CuSn12-B, CuAl10Fe2-B, CuAl10Fe2-B, CuAl10Ni5Fe4, CuAl10Fe5Ni5-B, CuMn11Al8Fe3Ni3-C, CuAl10Fe5Ni5-B, CuNi10Fe1Mn1-B, CuNi30Fe1 Mn1 NbSi—C, Cu-OFE, Cu—OF, CuAg0.05(OF), CuAg0.05(OF), CuAg0.05(OF), Cu-ETP, Cu-FRHC, CuAg0.05, CuAg0.1, Cu-DLP, CuAg0.1(P), Cu-DHP, Cu-FRTP, CuTe(P), CuCd1, CuBe1.7, CuBe2, CuCo2Be, CuNi2Be, CuZn5, CuZn10, CuZn15, CuZn15, CuZn20, CuZn30, CuZn30As, CuZn40, CuZn28Sn1, CuSn5, CuSn4, CuSn6, CuSn8, CuAl8Fe3, CuAl10Ni5Fe4, CuAl10Ni5Fe4, CuSi1, CuSi3Mn1, CuZn20Al2, CuNi1Si, CuNi10Fe1Mn, CuNi25, CuNi30Mn1Fe, CuNi30Mn1Fe, CuNi30Fe2Mn2, CuNi9Sn2, CuNi18Zn20, CuNi12Zn24, Cu—OF, CuAl10Ni5Fe4, CuAl7Si2, CuCr1Zr, CuNi10Zn42Pb2, CuNi2Si, CuSn0 CuSn5Zn5Pb5-C, CuPb5Sn5Zn5, CuZn30As, CuZn33Pb2-C, CuZn36Pb2As, CuZn36Pb2As, CuZn36Pb2As, CuZn36Pb3, CuZn36Pb3, CuZn36Sn1Pb, CuZn37, CuZn37Pb2, CuZn38Pb2, CuZn40Pb2, CuZn39Pb1, CuZn39Pb2, CuZn39Pb3, CuZn39Pb4, CuZn39Sn1, CuZn38Sn1, CuZn40Mn1Pb1FeSn, CuZn40Pb2, CuSn4Pb4Zn3, CuZn39Pb1Al—C, CuZn40Mn1Pb1AlFeSn and/or CuZn43Pb2Al.

Preferably, the layer is laterally non-conductive and vertically conductive.

Preferably the metal layer thickness is in the range of from 1 to 500 nm, preferably of from 1 to 400 nm. Preferably the layer thickness is at least 5 nm, more preferably at least 10 nm, yet more preferably at least 30 nm. The layer thickness preferably is at most 250 nm, more preferably at most 150 nm, and most preferably at most 100 nm.

For surgical drape or gown applications, the metal layer preferably is thin enough to provide the entire drape with a rigidity of less than about 60,000 kg·mm, preferably less than about 7,500 kg·mm, and most preferably less than about 0.1 kg·mm.

The present invention refers to fabric materials including woven or non-woven fabric and/or film surfaces.

Woven or nonwoven fabric materials are usually defined as sheet or web structures bonded together by entangling of fibres or filaments, and/or by perforating films mechanically, thermally or chemically. They are typically flat, porous, sheet like structures that are made from separate fibres, and/or from molten plastic or plastic film. Woven or nonwoven fabrics provide specific functions such as absorbency, liquid repellence, resilience, stretch, softness, strength, flame retardancy, washability, cushioning, filtering, use as a bacterial barrier and sterility.

Woven fabric according to the present invention may be formed from fibres Woven fabrics according to the invention are typically prepare from fibres and/or yarn prepared from fibres, such as synthetic fibres, natural fibres, or combinations thereof.

The process usually involves steps such as weaving or knitting, and it does not necessarily require converting fibres to yarn.

Synthetic fibres include, for example, polyester, acrylic, polyamide, polyolefin, polyaramid, polyurethane, regenerated cellulose, and blends thereof. More specifically, polyester includes, for example, polyethylene terephthalate, polytriphenylene terephthalate, polybutylene terephthalate, polylactic acid, and combinations thereof. Polyamide includes, for example, nylon-6, nylon-6.6, and combinations thereof. Polyolefins include polypropylene, polyethylene, and combinations thereof.

Polyaramid includes, for instance poly-p-phenyleneteraphthalamid (i.e., Kevlar (iD), poly-m-phenyleneteraphthalamid (i.e., Nomex (E)), and combinations or variations thereof.

Natural fibres include, for example, wool, cotton, flax, cellulose and blends thereof.

The fabric may be formed from fibres or yarns of any size, including microdenier fibres and yarns (fibres or yarns having less than one denier per filament). The fibres or yarns may have deniers that range from less than about 1 denier per filament to about 2000 denier per filament or more preferably, from less than about 1 denier per filament to about 500 denier per filament, or even more preferably, from less than about 1 denier per filament to about 300 denier per filament.

Furthermore, the fabric may be partially or wholly comprised of multi-component or bicomponent fibres or yarns which may be splittable along their length by chemical or mechanical action. The fabric may be comprised of fibres such as staple fibre, filament fibre, spun fibre, or combinations thereof.

The fabric may be of any variety, including but not limited to, woven fabric, knitted fabric, nonwoven fabric, or combinations thereof. They may optionally be coloured by a variety of dyeing techniques, such as high temperature jet dyeing with disperse dyes, thermosol dyeing, pad dyeing, transfer printing, screen printing, or any other technique that is common in the art for comparable, equivalent, traditional textile products. If yarns or fibres are treated by the process of the current invention, they may be dyed by suitable methods prior to fabric formation, such as, for instance, by package dyeing or solution dyeing, or after fabric formation as described above, or they may be left undyed.

The film may include thermoplastic materials, thermoset materials, or combinations thereof.

Thermoplastic or thermoset materials may include polyolefin, polyester, polyamide, polyurethane, acrylic, silicone, melamine compounds, polyvinyl acetate, polyvinyl alcohol, nitrile rubber, ionomers, polyvinyl chloride, polyvinylidene chloride, chloroisoprene, or combinations thereof. The polyolefin may be polyethylene, polypropylene, ethylvinyl acetate, ethylmethyl acetate, or combinations thereof. Polyethylene may include low density or high density polyethylene. The film may have a thickness of between 1 and 500 μm, preferably between 2 μm and 250 μm, or even more preferable between about 3 and 100 μm.

Typically, the process to prepare a non-woven fabric does not involve process steps such as weaving or knitting, and it does not require converting fibres to yarn, and yarn to fabric. Nonwoven fabrics may be engineered for a single use, limited life or a durable fabric.

The nonwoven fabric material preferably is a nonwoven web which may include nonwoven webs manufactured by any of the commonly known processes for producing nonwoven webs. As used herein, the term “nonwoven web” refers to a fabric that has a structure of individual fibres or filaments which are randomly and/or unidirectionally interlaid in a mat-like fashion.

For example, the fibrous nonwoven web can be made by carded, air laid, wet laid, spunlaced, spunbonding, electrospinning or melt-blowing techniques, such as melt-spun or melt-blown, or combinations thereof. Spunbonded fibres are typically small diameter fibres that are formed by extruding molten thermoplastic polymer as filaments from a plurality of fine, usually circular capillaries of a spinneret with the diameter of the extruded fibres being rapidly reduced. Meltblown fibres are typically formed by extruding the molten thermoplastic material through a plurality of fine, usually circular, die capillaries as molten threads or filaments into a high velocity, usually heated gas (e.g., air) stream which attenuates the filaments of molten thermoplastic material to reduce their diameter. Thereafter, the meltblown fibres are carried by the high velocity gas stream and are deposited on a collecting surface to from a web of randomly disbursed meltblown fibres. Any of the non-woven webs may be made from a single type of fibre or two or more fibres that differ in the type of thermoplastic polymer and/or thickness.

Staple fibres may also be present in the web. The presence of staple fibres generally provides a loftier, less dense web than a web of only melt blown microfibers. Preferably, no more than about 20 weight percent staple fibres are present, more preferably no more than about 10 weight percent. Webs containing such staple fibre are for instance disclosed in U.S. Pat. No. 4,118,531.

The nonwoven fabric may advantageously be fashioned or shaped in any suitable article. Such an article may optionally further comprise one or more layers of scrim. For example, either or both major surfaces may each optionally further comprise a scrim layer. The scrim, which is typically a woven or nonwoven reinforcement made from fibres, is included to provide strength to the nonwoven article. Suitable scrim materials include, but are not limited to, nylon, polyester, fibreglass, and the like. The average thickness of the scrim can vary. Typically, the average thickness of the scrimranges from about 25 to about 100 μm, preferably about 25 to about 50 μm. The layer of the scrim may optionally be bonded to the nonwoven article. A variety of adhesive materials can be used to bond the scrim to the polymeric material. Alternatively, the scrim may be heat-bonded to the nonwoven. The micro fibres of the nonwoven fabric material substrate typically have an effective fibre diameter of from about 0.5 to 15 μm, preferably from about 1 to 6 μm, as calculated according to the method set forth in Davies, C. N., “The Separation of Airborne Dust and Particles,” Institution of Mechanical Engineers, London, Proceedings IB, 1952.

The nonwoven fabric material preferably has a basis weight in the range of about 10 to 400 g/m², more preferably about 10 to 100 g/m². The average thickness of the nonwoven fabric material is preferably about 0.1 to 10 mm, more preferably about 0.25 to 5 mm for the non-functionalized, uncalendared fabric material.

The minimum tensile strength of the nonwoven web is at least 3.0, preferably at least 4.0 Newtons. It is generally recognized that the tensile strength of nonwovens is lower in the machine direction than in the cross-web direction due to better fibre bonding and entanglement in the latter.

Nonwoven web loft is measured by solidity, a parameter that defines the solids fraction in a volume of web. Lower solidity values are indicative of greater web loft. Useful nonwoven fabric materials typically have a solidity of less than 20%, preferably less than 15%, as defined in WO-A-2010151447. Solidity is used herein to refer to the nonwoven fabric material itself and not to the functionalized nonwoven. When a nonwoven fabric material contains mixtures of two or more kinds of fibres, the individual solidities are determined for each kind of fibre using the same L[nonwoven] and these individual solidities are added together to obtain the web's solidity, dt.

As an example, the nonwoven fabric material before calendering or grafting preferably has an average pore size of 14 μm, calculated from a thickness of 0.34 mm, effective fibre diameter of 4.2 um and solidity of 13%. After calendering the nonwoven web will have a thickness of 0.24 mm and solidity of 18% with an average pore size of 8 μm. The term “average pore size”, also referred to as average pore diameter is related to the arithmetic median fibre diameter and web solidity and can be determined as disclosed in WO-A-2010/151447.

The nonwoven fabric material preferably has a mean pore size of 1-40 μm, preferably 2-20 μm. Mean pore size may be measured according to ASTM F 316-03 “Standard Test Methods for Pore Size Characteristics of Membrane Filters by Bubble Point and Mean Flow Pore Test Method B” using Freon TF™ as the test fluid. The nonwoven fabric material may be formed from any suitable thermoplastic polymeric material. Suitable polymeric materials include, but are not limited to, polyolefins, poly(isoprenes), poly(butadienes), fluorinated polymers, chlorinated polymers, polyamides, polyimides, polyethers, poly(ether sulfones), poly(sulfones), poly(vinyl acetates), copolymers of vinyl acetate, such as poly(ethylene)-co-poly(vinyl alcohol), poly(phosphazenes), poly(vinyl esters), poly(vinyl ethers), poly(vinyl alcohols), and poly(carbonates).

Suitable polyolefins include, but are not limited to, poly(ethylene), poly(propylene), poly(1-butene), copolymers of ethylene and propylene, alpha olefin copolymers (such as copolymers of ethylene or propylene with 1-butene, 1-hexene, 1-octene, and 1-decene), poly(ethylene-co-1-butene) and poly(ethylene-co-1-butene-co-1-hexene).

Suitable fluorinated polymers include, but are not limited to, poly(vinyl fluoride), poly(vinylidene fluoride), copolymers of vinylidene fluoride (such as poly(vinylidene fluoride-co-hexafluoropropylene), and copolymers of chlorotrifluoroethylene (such as poly(ethylene-co-chlorotrifluoroethylene).

Suitable polyamides include, but are not limited to, nylon 6, nylon 6,6, nylon 6, 12 poly(iminoadipoyliminohexamethylene), poly(iminoadipoyliminodecamethylene), and polycaprolactam. Suitable polyimides include poly(pyromellitimide). Suitable poly(ether sulfones) include, but are not limited to, poly(diphenylether sulfone) and poly(diphenylsulfone-co-diphenylene oxide sulfone).

Suitable copolymers of vinyl acetate include, but are not limited to, poly(ethylene-co-vinyl acetate) and such copolymers in which at least some of the acetate groups have been hydrolyzed to afford various poly(vinyl alcohols) including, poly(ethylene-co-vinyl alcohol).

Preferred polymers are inherently hydrophilic and are readily grafted by ionizing radiation, such as by exposure to e-beam or gamma radiation. Preferred polymers include of polyamides and ethylene vinyl alcohol polymers and copolymers.

For surgical drapes or gowns or similar apparel, preferred nonwoven fabric sheets are made from wood pulp; fibres of a thermoplastic polymeric material, including melt-blown polymer fibres, such as melt-blown polypropylene fibres, and synthetic polymer fibres, such as polypropylene, polyester, polyethylene, polyolefin, polyamide and nylon fibres; cellulosic nonwoven fibres such as nonwoven rayon; and combinations of these materials.

The term “thermoplastic” is used herein to refer to materials which are solid at room temperature, i.e. from 22° C. to 30° C., but which soften or melt when heated to temperatures above room temperature. Thermoplastic materials are extrudable at temperatures in excess of 50° C. Preferred thermoplastic materials soften or melt at temperatures above about 50° C. and below about 1,000° C., in order that the material will not melt during transportation but be melted by commonly-used surgical lasers. More preferred thermoplastic materials soften or melt at temperatures between 60° C. and 500° C. For surgical drape applications where patient comfort is a factor, preferably at least 10 percent of the nonwoven fibres have lengths greater than about 0.06 cm.

Preferred nonwoven fabric sheets include a layer of polyethylene film sandwiched between two layers of nonwoven rayon (commercially available as “Steri-Drape® Blue Fabric” from 3M Company, Saint Paul, Minn.); melt-blown polypropylene fabric; and a combination of wood pulp and polyester fibres (commercially available as “Assure® I, II, or III Nonwoven Fabric” from Dexter Corporation, Windsor Locks, Conn.). A further preferred non-woven material is hydroentangled SONTARA® (a registered trade mark of the DuPont Corporation, Delaware).

Nonwovens are typically manufactured by putting small fibres together in the form of a sheet or web, and then binding them either mechanically (as in the case of felt, by interlocking them with serrated needles such that the inter-fibre friction results in a stronger fabric, with an adhesive; thermally; by applying binder, preferably in the form of powder, paste, or polymer melt, and then melting the binder onto the web by increasing temperature.

The nonwoven fabric material may be a nonwoven web, paper, film, foam, elastomeric material, which may be supplied with the antimicrobial composition.

If the nonwoven fabric has a weblike structure, it may preferably be a spunbond web, meltblown web, bonded carded web, airlaid web, coform web, and/or hydraulically entangled web.

Polymers suitable for making nonwoven webs include, for example, polyolefins, polyesters, polyamides, polycarbonates, copolymers and blends thereof, etc. Most embodiments of the laminate of the present invention employ a nonwoven web formed from olefin-based polymers, which are non-polar in nature. Suitable polyolefins include polyethylene, such as high density polyethylene, medium density polyethylene, low density polyethylene, and linear low density polyethylene; polypropylene, such as isotactic polypropylene, atactic polypropylene, and syndiotactic polypropylene; polybutylene, such as poly(1-butene) and poly(2-butene); polypentene, such as poly(1-pentene) and poly(2-pentene); poly(3-methyl-1-pentene); poly(4-methyl-1-pentene); and copolymers and blends thereof. Suitable copolymers include random and block copolymers prepared from two or more different unsaturated olefin monomers, such as ethylene/propylene and ethylene/butylene copolymers.

Such polymer(s) may preferably also contain additives, such as processing aids to impart desired properties to the fibres, residual amounts of carriers, pigments or colorants, and so forth.

If desired, the nonwoven fabric may have a multi-layer structure. Suitable multi-layered materials may include, for instance spunbond/meltblown/spunbond (SMS) laminates and spunbond/meltblown (SM) laminates. Various examples of suitable SMS laminates are described in U.S. Pat. No. 4,041,203, U.S. Pat. No. 5,213,881, U.S. Pat. No. 5,464,688, U.S. Pat. No. 4,374,888 U.S. Pat. No. 5,169,706 and U.S. Pat. No. 4,766,029. Nonwoven fabric materials are usually made in at least two steps. In a first step, fibres are cut to a few centimetres length, and then dispersed on a conveyor belt, where they are spread in a uniform web by a wetlaid process or by carding. Combining melt blown and spunbond fibres results in SM or SMS webs nonwoven fabric materials, which are strong and offer the intrinsic benefits of fine fibres such as fine filtration, low pressure drop as used in face masks or filters and physical benefits such as acoustic insulation as used in dishwashers, for instance for disposable diaper and hygiene care products.

Melt blown non woven fibres are typically produced by extruding melted polymer fibres through a spin net or die to form long thin fibres which are stretched and cooled by passing hot air over the fibres as they fall from the die. The resultant web is collected into rolls and subsequently converted to finished products. The extremely fine fibres typically differ from other in that they have low intrinsic strength but much smaller size offering.

Nonwoven fabrics are typically bonded by using either resin or thermally. Bonding can be throughout the web by resin saturation or overall thermal bonding or in a distinct pattern via resin printing or thermal spot bonding.

The nonwoven fabric may advantageously also contain additional fibrous components. For example, a nonwoven fabric may be entangled with a fibrous component using any of a variety of entanglement techniques known to a person skilled in the art, such as cellulosic fibres or glass fibres. A typical hydraulic entangling process utilizes high pressure jet streams of water to entangle fibres to form a highly entangled consolidated fibrous structure, e.g., a nonwoven fabric. Fibreglass is wetlaid into mats for use in roofing and shingles. Synthetic fibre blends are wetlaid along with cellulose for single-use fabrics.

Hydraulically entangled nonwoven fabrics are disclosed for instance in U.S. Pat. No. 3,494,821 and U.S. Pat. No. 4,144,370, U.S. Pat. No. 5,284,703 and U.S. Pat. No. 6,315,864.

Other materials may also be used to form the nonwoven fabric material. For example, the nonwoven fabric may contain an elastomeric polymer, such as natural rubber latex, isoprene polymers, chloroprene polymers, vinyl chloride polymers, styrene-ethylene-butylene-styrene block copolymers, styrene-isoprene-styrene block copolymers, styrene-butadiene-styrene block copolymers, styrene-isoprene block copolymers, styrene-butadiene block copolymers, butadiene polymers, styrene-butadiene polymers, carboxylated styrene-butadiene polymers, acrylonitrile-butadiene polymers, carboxylated acrylonitrile-butadiene polymers, acrylonitrile-styrene-butadiene polymers, carboxylated acrylonitrile-styrene-butadiene polymers, derivatives thereof, and so forth. The fabric material may optionally be treated with liquid-repellency additives, antistatic agents, surfactants, colorants, antifogging agents, fluorochemical blood or alcohol repellents, and/or lubricants.

The woven or non-woven fabric materials according to the present invention can be prepared particularly cheaply and in large economical scale with high throughput processes, giving access to comparatively cheap antimicrobial products that may be employed for applications where prior to the invention the use of antimicrobial materials would have been unsuccessful due to the prohibitive costs involved. The metal composition may be tailored according to the use and potential contamination targeted. The economics can be maintained due to the extremely low amounts of metal deposited. The metal layer has a high adhesion, while other properties, such as flexibility of the substrate, remain unchanged.

The metal layer on the woven or non-woven fabric is preferably applied by a vacuum metalizing process, more preferably by a physical vapour deposition (PVD) process. This term describes a thermal evaporation process for evaporating metals inside a vacuum chamber which then bond to the desired fabric material to achieve a uniform metalized layer. Thermal evaporation is the most common process used to apply metal alloys under vacuum. Other physical vapour deposition processes include sputtering and ion-plating. Magnetron sputtering is the most utilized sputtering deposition method for thin metal films. This plasma assisted method provides deposition of a large number of various materials, including metal and alloys. However, films obtained by sputtering methods have generally polycrystalline structures with columnar grains, thereby reducing the available surface area of the metal atoms. Similary, ion plating is not considered a suitable process for the preparation of the meta layers according to the subject invention.

In contrast, the present metal layer is preferably prepared by a physical vapour depositions using a heated metal source instead of an ion sources. This method permits to create a high quality metal film with a high active surface metal area. This process comprises heating a metal vapour source under reduced pressure of at, or of less than or below 7.0×10⁻³, to generate a metal vapour, and (ii) depositing the vapour on a substrate.

Optionally, a coating may be applied as a base coat prior to the metalizing process to increase adhesion, or increase the smoothness of the fabric material. Also optionally, a coating may be applied to the metal layer if the substrate needs to possess printability after metallisation of where aesthetic aspects are important.

The vacuum metalizing process typically comprises the following steps: (a) producing a (high) vacuum in a vacuum chamber at or below 7.0×10⁻³ mbar, preferably at or below 1.0×10⁻⁴ mbar; (b) optionally metering a predetermined amount of inert gas into the vacuum chamber to provide a higher pressure than the high vacuum, (c) evaporating and depositing a metal or metal alloy on the fabric material in the vacuum chamber, and (d) removing the nonwoven fabric material substrate from the vacuum chamber. In the subject process, the fabric is exposed to metal vapour in a high vacuum, usually under ambient conditions.

A suitable apparatus for the vacuum deposition of a metal coating on a fabric according to the present invention are those disclosed for instance in GB-A-774 439, GB-A-796 138, U.S. Pat. No. 4,844,009 and WO-A-2005/045093.

The subject woven and non-woven antimicrobial materials may advantageously be employed in various applications to inhibit the growth of microorganisms. For example, they may be used in treatments or surroundings where hospital-acquired infections caused by bacteria, viruses, fungi, or parasites. The subject woven and non-woven antimicrobial materials preferably have an antibacterial activity of at least 3, more preferably at least 4, yet more preferably at least 5 as determined by the ISO 20743:2007 method, using Staphylococcus aureus ATCC 6538 and/or Klebsiella pneumoniae ATCC 4352. This activity is advantageously measured on the on the metalized surface as described herein below.

Antimicrobial woven and non-woven fabric materials according to the invention may advantageously be employed in numerous applications, including: hygiene articles, such as diapers, feminine hygiene articles, wet wipes, bandages, facial masks and wound dressings; medical isolation and/or surgical apparel and gowns, surgical drapes and covers, surgical scrub suits, masks, caps and generally disposable clothing; filters for fluids and air, sensitive packaging materials and so on. These filters are typically employed in filtration and processing steps in the pharmaceutical, chemical, food and mineral and oil processing industry, and may be formed into cartridge and bag filters, vacuum bags, allergen membranes.

The present invention further also relates to a metallised woven or non-woven fabric material such as sheet cloth and its applications as part of a filter cartridge. Filters in HVAC systems providing physical separation ability can be enhanced with antibacterial features according to the process of the present invention. The effect is desirable in high quality air environments such as hospitals and health care facilities, but also public spaces, such as preferably public transport, e.g. underground trains, large office buildings, schools, housing and the like. The present invention further relates to a filter comprising the metallised non-woven material with bacterial growth suppressing activity. The filter, and cartridges comprising the nonwoven fabric material according to the invention may be employed for air and/or liquid filtration, such as for instance for drinking water. In the latter it may advantageously remove smells, discolouration and chemical contaminants such as chlorine besides its antimicrobial function. The antibacterial filter comprising material according to the invention can further positively reduce the microbial load, and hence impact air quality in stand-alone ventilation circuits in the automotive and aerospace industries.

The woven non-woven fabric may be used alone, or in combination with other materials for a further spectrum of products with diverse properties, such as components of apparel, home furnishings, health care, engineering, industrial and consumer goods. In addition, the (non)woven fabric material substrate may also serve other purposes, such as providing water absorption, barrier properties, etc. Any of a variety of (non)woven fabric material substrates may be applied with the antimicrobial composition in accordance with the present invention. Accordingly, the present invention also relates to the use of the materials according to the invention, or those materials obtainable according to above described process, for the control or restriction of antimicrobial growth.

Although several specific embodiments of the present invention have been described in the detailed description above, this description is not intended to limit the invention to the particular form or embodiments disclosed herein since they are to be recognised as illustrative rather than restrictive, and it will be obvious to those skilled in the art that the invention is not limited to the examples.

EXAMPLES General Antibacterial Assay

The antibacterial activities of cellulosic non-woven sheet materials according to the invention were tested against reference non-coated sheet materials in the effectiveness to inhibit the growth of Gram-negative Escherichia coli as well as against the Gram-positive Staphylococcus aureus (S. aureus, specifically methicilin-resistant staphylococcus aureus (MRSA) bacteria), applying the ISO 20743:2007 method. The ISO 20743:2007 method is a quantitative test method to determine the antibacterial activity of antibacterial finished textile products including nonwovens.

For the experiments, two cellulose base materials were used, (Example 1) on the basis of the hydroentangled SONTARA® (a registered trade mark of the DuPont Corporation), a non woven fabric material that is commonly used as wipes, and in health care applications as gowns; and (Example 2) a non woven material which is the basis for multiple applications including facial masks).

Example 1 Antimicrobial Activity

Non-woven materials were vacuum metallised with various Ag—Cu—Al alloys, and the obtained materials subjected to anti-bacterial tests according to ISO 20743:2007(Textiles—Determination of antibacterial activity of antibacterial finished products). This test is used to quantitatively measure the antimicrobial activity of antibacterial finished textile products including nonwovens.

Strains tested were: Staphylococcus aureus ATCC 6538 and Klebsiella pneumoniae ATCC 4352.

Method and principle of the test: Treated samples and control samples are cut in pieces of 3.8 cm diameter. The inoculation is achieved by transfer of bacteria from an agar plate onto samples: Each sample (as well as each control) is placed on the agar surface of an agar plate that has been previously inoculated (by first flooding the agar surface with 1 ml of a bacterial suspension adjusted to a concentration of 1×10⁶ to 3×10⁶ CFU/ml and then sucking up as much of the excess liquid as possible).

The volume of the inoculum used to flood the agar surface of the transfer agar plate is 1 ml. The composition of the inoculum solution was as follows:

Peptone-Salt solution (Tryptone, pancreatic digest of casein 1 g/l, NaCl 8.5 g/l)−Volume of the extraction solution (=neutralizing solution): 20 ml

Composition of the neutralizing solution: Polysorbate 80 30 g/l; Lecithin 3 g/l; Histidine hydrochloride 1 g/l, Peptone 1 g/l, NaCl 4.3 g/l; Monopotassium phosphate 3.6 g/l, Disodium phosphate dihydrate 7.2 g/l.

Then a weight of 200 g was applied on the sample for 60 seconds and the sample is afterwards placed in a Petri dish with the transferred surface face up.

Six test samples in individual Petri dishes plus six separate Petri dishes with control samples constituted one test. Immediately after transfer (“0 contact time”) three of the six samples and three of the six controls are placed in a vial containing a neutralizing solution (1 vial/sample) and are shaken out to extract the bacteria present on them. Counting on the extraction liquid was performed by the Plate Count Method.

The other samples and controls were incubated in their Petri dishes in a humidity chamber at 37° C. for 18 to 24 hours.

After incubation, extractions and counting of the bacteria still present on the remaining samples (3 treated and 3 controls) were performed as for “0 contact time”. The growth value and the activity values were then computed:

The growth value is computed as followed:

F=C _(t) −C ₀

Where F: growth value on the control sample

C_(t): average common logarithm for the number of bacteria obtained from three test samples of control fabric after 18 to 24 hours incubation

C₀: average common logarithm for the number of bacteria obtained from three test samples of control fabric immediately after transfer to the control fabric.

The test is judged to be effective, if the growth value is equal or above 1 and when the difference in extremes for the three controls immediately after transfer as well as after incubation is equal or below log₁₀

The calculation of the activity is obtained according to the following formula:

A=(C _(t) −C ₀)−(T _(t) −T ₀)=F−G

Where: A: antibacterial activity value

F: growth value on the control fabric (F=C_(t)−C₀)

G: growth value on the antibacterial treated sample (G=T_(t)−T₀)

T_(t): average common logarithm for the number of bacteria obtained from three antibacterial treated test samples after 18 to 24 hours incubation

T₀: average common logarithm for the number of bacteria obtained from the antibacterial treated test samples according to the invention immediately after transfer.

The bacteria were transferred onto the “metalized side” of the sample for the treated samples. The samples were not sterilized before performing the test; The colony-forming unit of viable bacterial cell numbers (CFU) was measured, and the results were as follows (Tables 1 to 6):

TABLE 1 Antibacterial Activity by evolution of number of viable cells [Log CFU] Initial Count count after 18 h Layer Appear- [Log [Log Metal Layer Thickness ance CFU/g] CFU/g] Sample A Ag/Cu 30/70 150 nm Gray 4.2 0 alloy (wt/wt) Sample B Cu 150 nm Red 4.2 0 Example C Al/Cu 85/15 150 nm Gray 4.2 0 alloy (wt/wt) Comparative No metal — n.d. 4.6 7.1 Example

Example 2

Example 1 was repeated with a different non-woven tissue substrate.

TABLE 2 Sample identification Identification number Description of the samples** Comparative 1 Non-woven tissue without vacuum metal layer Sample 1 Non-woven tissue with vacuum metal layer of Al/Cu 85/15 alloy Sample 2 Non-woven tissue with vacuum metal layer of Cu/Ag 70/30 alloy Comparative 2 Non-woven tissue without vacuum metal layer Sample 3 Non-woven tissue with vacuum metal layer Al/Cu 85/15 alloy Sample 4 Non-woven tissue with vacuum metal layer of Cu/Ag 70/30 alloy EMPA Cotton 100% Internal Control sample, Untreated* *This control was added in order to check the growth and the behaviour of the bacterial strain **The metal layer thickness was 150 nm in all examples; ratio of metals in the alloy are given as wt/wt

TABLE 3 Control of the growth value obtained on the internal control sample and on the untreated samples with Methicillin Resistant Staphylococcus aureus—MRSA; Contact time: 18 hours, Inoculum concentration: 1.68 10⁶ CFU/ml. Number of viable cells Number of viable cells at Contact time = 0* at Contact time = 18 h* Sample ID Trial CFU Log CFU CFU Log CFU Internal 1 9.6 × 10⁴ 4.95 7.4 × 10⁷ 7.87 Control 2 1.2 × 10⁵ 5.07 5.8 × 10⁷ 7.76 EMPA 3 1.0 × 10⁵ 5.01 5.6 × 10⁷ 7.75 Cotton 100% Average   5 ± 0.05 7.8 ± 0.05 (log) Growth  2.8** Value F Comparative 1 9.4 × 10⁴ 4.95 7.0 × 10⁷ 7.85 Sample 1 2 2.2 × 10⁵ 5.07 6.8 × 10⁷ 7.83 3 1.1 × 10⁵ 5.01 5.0 × 10⁷ 7.70 Average 5.1 ± 0.2 7.8 ± 0.08 (log) F 2.7 Comparative 1 1.5 × 10⁵ 4.95 7.4 × 10⁷ 7.87 Sample 2 2 8.2 × 10⁴ 5.07 5.8 × 10⁷ 7.76 3 1.0 × 10⁵ 5.01 5.6 × 10⁷ 7.75 Average   5 ± 1.4 7.8 ± 0.05 (log) F 0.9 *Colonies expressed per sample; **The growth value is equal or above 1 for the Internal Control fabric sample, thus test is operative. The same applies to Comparative sample 1; for the second comparative sample, due to a single outlier, the growth value was slightly too low (0.9).

TABLE 4 Count of the untreated samples with Methicillin Resistant Staphylococcus aureus—MRSA; Contact time: 18 hours, Inoculum Concentration: 1.68 10⁶ CFU/ml Number of viable cells Number of viable cells at Contact time = 0* at Contact time = 18 h* Sample ID Trial CFU Log CFU CFU Log CFU Sample 1 1 1.6 × 10⁵ 5.19  0** 0 2 1.9 × 10⁵ 5.28 2.8 × 10² 2.45 3 1.3 × 10⁵ 5.11 0 0 Average 5.2 ± 0.09 0.8 ± 1.41 (log) Growth −4.4 Value F Sample 2 1 1.1 × 10⁵ 5.05 1.2 × 10² 2.08 2 8.6 × 10⁴ 4.93 0 0 3 1.0 × 10³ 3.01 2.0 × 10¹ 1.30 Average 4.3 ± 1.14 1.1 ± 1.05 (log) F −3.2 Sample 3 1 1.5 × 10⁵ 5.11  0** 0 2 8.2 × 10⁴ 5.34 0 0 3 1.0 × 10⁵ 5.10 0 0 Average   5 ± 0.14 0 (log) F −4.3 Sample 4 1 1.4 × 10⁵ 5.16 0 0 2 3.2 × 10⁴ 4.51 0 0 3 7.0 × 10⁴ 4.85 0 0 Average 4.8 ± 0.33 0 (log) F −4.8 *Colonies expressed per sample; **No colony has been counted; log CFU as been arbitrarily fixed to 0 in this case.

The Mean Antibacterial activity [A] was found as follows (Table 5):

TABLE 5 Mean Antibacterial Activity A after 18 hours Mean [A] Sample 1 7.1 Al/Cu 85/15 Sample 2 5.9 Cu/Al 70/30 Sample 3 5.2 Al/Cu 85/15 Sample 4 5.7 Cu/Al 70/30

Example 3 Results Obtained with Klebsiella pneumoniae

Examples 1 and 2 were repeated with Klebsiella pneumoniae, see Tables 6 and 7.

TABLE 6 Control of the growth value obtained on the internal control sample and on the untreated samples with Klebsiella pneumoniae - Contact time: 18 hours, Inoculum concentration: 2.7 × 10⁶ CFU/ml Number of viable cells Number of viable cells at Contact time = 0* at Contact time = 18 h* Sample ID Trial CFU Log CFU CFU Log CFU Internal 1 3.4 × 10⁴ 4.53 2.4 × 10⁸ 8.38 Control 2 5.0 × 10⁵ 4.70 2.0 × 10⁸ 8.30 EMPA 3 3.2 × 10⁵ 4.51 1.9 × 10⁸ 8.27 Cotton 100% Average 4.6 ± 0.1  8.3 ± 0.06 (log) Growth 3.7 Value F Comparative 1 1.3 × 10⁵ 5.11 2.2 × 10⁸ 8.34 Sample 1 2 7.6 × 10⁴ 4.88 2.0 × 10⁸ 8.30 3 5.8 × 10⁴ 4.76 2.0 × 10⁸ 8.30 Average 4.9 ± 0.18 8.3 ± 0.02 (log) F 3.4 Comparative 1 6.2 × 10⁴ 5.11 5.2 × 10⁷ 7.72 Sample 2 2 1.3 × 10⁵ 4.88 1.5 × 10⁸ 8.17 3 5.0 × 10⁴ 4.76 1.3 × 10⁸ 8.13 Average 4.9 ± 0.21   8 ± 0.25 (log) F 3.1 *Colonies expressed per sample; **The growth value was equal or above 1 for all controls

TABLE 7 Count of Klebsiella pneumoniae on the samples - Contact time: 18 hours, Inoculum concentration: 2.7 10⁶ CFU/ml Number of viable cells Number of viable cells at Contact time = 0* at Contact time = 18 h* Sample ID Trial CFU Log CFU CFU Log CFU Sample 1 1 2.4 × 10⁵ 5.38 4.0 × 10¹ 1.60 2 7.4 × 10⁴ 4.87 2.0 × 10¹ 1.30 3 5.2 × 10⁴ 4.72 2.0 × 10¹ 1.30 Average   5 ± 0.35 1.4 ± 0.17 (log) Growth −3.6 Value F Sample 2 1 3.2 × 10³ 3.51 4.0 × 10¹ 1.60 2 7.0 × 10² 2.85 0 0 3 2.4 × 10³ 3.38 8.0 × 10¹ 1.90 Average 3.2 ± 0.35 1.2 ± 1.02 (log) F −2   Sample 3 1 8.8 × 10⁴ 3.51 1.1 × 10³ 3.06 2 1.0 × 10⁵ 2.85 6.6 × 10³ 3.82 3 1.1 × 10⁵ 3.38 8.0 × 10¹ 1.90 Average   5 ± 0.05 2.9 ± 0.97 (log) F −2.1 Sample 4 1 7.4 × 10³ 3.87 2.0 × 10¹ 1.30 2 2.4 × 10³ 3.38 0 0 3 1.1 × 10⁴ 4.03 0 0 Average 3.8 ± 0.34 0.4 ± 0.75 (log) F −3.4 *Colonies expressed per sample, **No colony has been counted; log CFU as been arbitrarily fixed to 0 in this case.

TABLE 6 Mean Antibacterial activity after 18 hours Mean [A] Sample 1 7 Al/Cu 85/15 Sample 2 5.4 Cu/Al 70/30 Sample 3 5.2 Al/Cu 85/15 Sample 3 6.5 Cu/Al 70/30

The above examples above clearly illustrate the extremely high antimicrobial activity of the materials according to the present invention. 

1. A fabric material having antimicrobial activity, the fabric material comprising: (a) a fabric layer comprising at least one of a woven and a non-woven fabric material; and (b) a non-conductive metal layer deposited onto the fabric layer, the non-conductive metal layer having a thickness in the range of 1 to 500 nm, wherein the metal layer comprises at least one of copper and silver.
 2. A material according to claim 1, wherein the metal layer comprises at least one of copper and a copper alloy.
 3. The material according to claim 1, wherein the fabric layer has a weight in the range of 40 to 300 grams per square meter.
 4. The material according to claim 1 wherein the antimicrobial metal layer has weight in the range of 0.15 grams to 100 grams per square meter.
 5. The material according to claim 1, wherein the fabric layer comprises fibers having an average fiber size of from 0.7 μm to 0.1 cm.
 6. The material according to claim 1, wherein the fabric layer has a void volume in the range of from 50 to 95%.
 7. The material according to claim 1, wherein the fabric layer has a tensile strength of at least 3.0 Newton prior to metal deposition.
 8. The material according to claim 1, having a surface area of 15 to 50 square meters.
 9. The material according to claim 1, wherein the fabric layer has a mean pore size in the range of 1-40 μm as determined according to ASTM F 316-03
 5. 10. The material according to claim 1, wherein the fabric layer has a solidity of less than 20%.
 11. The material according to claim 1, wherein the nonwoven fabric material is a spunlaid, spunlaced, hydroentangled, electrospun or meltblown nonwoven fabric material.
 12. The material according to claim 1 having a mean antibacterial activity of at least 3, the mean antibacterial activity being determined according to ISO 20743:2007.
 13. An article including any one of a surgical drape, a facial mask, surgical clothing, wound dressing, or a filter element, the article comprising: an antimicrobial nonwoven fabric having a fabric layer and a metal layer, said metal layer deposited on at least one side of the fabric layer, wherein the metal layer comprises at least one of copper and silver.
 14. A process for the preparation of a fabric material having antimicrobial activity, the fabric material comprising a woven material or a nonwoven material, the process comprising the step of: depositing, via thermal evaporation metal vacuum deposition, a metal layer on at least one side of the fabric material, the metal layer comprising at least one of copper and a copper alloy.
 15. A process according to claim 14, wherein the metal layer has a thickness in the range of 1 to 500 nm determined according to an ICP-OES analysis.
 16. A process according to claim 14, further comprising the steps of: (a) reducing a pressure in a vacuum chamber to at or below 7.0×10⁻³ mbar; (b) evaporating and depositing the at least one of copper and a copper alloy on the fabric material in the vacuum chamber; and (c) removing the fabric material from the vacuum chamber.
 17. A method for controlling antimicrobial growth on a fabric material, said fabric material comprising a woven or nonwoven material, the method comprising the step of: depositing an antimicrobial material onto the fabric material, wherein the antimicrobial material is a metallic non-conductive component comprising at least one of copper and silver.
 18. The method according to claim 14 wherein said fabric material is a sheet suitable for use as a surgical drape. 